1. Field of Invention
This invention relates to electronic timers and photoelectric controllers used to control electric lighting, activate animal feeders, control irrigation, or other timed control activation apparatus, where daylight sensing is used as a timing cue.
2. Discussion of Prior Art
Electric or electronic timer apparatus often used for controlling devices need to be set with the proper time, both initially and upon replacing a battery or after the time wanders for some reason. In some applications, having to set the time could require that personnel reach inaccessible places.
Another class of device controllers operates on sensing daylight. Where timing is based relative to the amount of ambient daylight, these prior art device controllers do not employ an internal time clock. They rely upon the natural cycle of the day and night. The driving function of these controllers, after all, is the amount of light, not the absolute time.
Photoelectric controls have long been used to sense daylight and activate a switch based upon the amount of light intensity measured by the photoelectric xe2x80x98eyexe2x80x99. Streetlights and other outdoor lighting have been controlled by employing low-cost circuits. The photoelectric light controls save energy by only activating the lamps when it is dark. Furthermore, it occurs automatically and does not require human intervention.
In the application of prior art utilized for outdoor lighting, there are some disadvantages to the way these controls function. The controls in such lighting employ a delay function so that the lamp is less likely to be falsely started. This works sufficiently well, much of the time. It still occurs that a lamp will be activated when a stormy cloudcover forms temporarily. This occasional occurrence with old methods has an associated cost, and this is a disadvantage of the prior art.
Because of the cost of energy and cost of wear-and-tear on the lamp every time a lamp is started unnecessarily, the cost can be significant over time. For yard lighting, the photoelectric controls are often used with one controller on each lamp in the yard. Since changing the lightbulb may require the utilization of a ladder, the homeowner would appreciate the advantage of increasing the life of the bulb.
Photoelectric controls have also long been used in animal feeder devices. A simple circuit detects light intensity and triggers a motor to run when the light intensity increases over a given threshold, at sunrise. The motor causes feed to be distributed on the ground for game to eat. Similarly at sunset, detection of the decrease in light intensity below a threshold triggers a feeding by activating the feed motor. The prior art typically uses, at most, only three functions:
a. measurement of ambient light intensity;
b. measurement of the rate of change of ambient light intensity;
c. time delay (on the order of time less than one hour).
One disadvantage of this method is that occasionally the feeder will be triggered in response to light intensity changes due to clouds rolling by. This disrupts the feeding pattern, wastes food, and lessens battery life. Another disadvantage is that it is desirable to feed the game before the sun goes down, while there is still ample hunting light. To trigger the feeder based on light intensity alone or change in light intensity, it is impossible to get the circuit to consistently feed a fixed time before the sun goes down. By introducing time delay in the circuit to attempt to reduce the occurrence of false triggers, this results in the sundown feeding occurring after dark. To the hunter, this is a disadvantage.
Sometimes another time delay function is added. There have been some attempts in prior art to cause an animal feeder device to feed before sundown. The intention is to encourage a foraging pattern among the game animals such that they are out during times of ample hunting daylight. While it is desirable to feed game about an hour before sundown, the prior art could not effectively accomplish this. The simplistic method employed in the prior art was to start an electronic timer upon sunrise, which caused a feeding to occur a given fixed amount of hours after sunrise when the timer timed-out. The inferior performance of this prior method is exemplified here. Assume employment of a fixed time delay of 9 hours after sunrise. At some latitude, this may cause the afternoon feeding to occur about an hour before sundown in December, but the feeding would occur six hours before sundown in June.
A similar additional time delay has sometimes been added to photoelectric lighting controls. The added function of keeping lights on for a set period of time, after sunset, has been employed. Adding a fixed time delay function is not affective  effective in providing the service of activating lights one hour before sunrise, for instance. This is another disadvantage of prior art device controllers. The means of anticipation of the event of sunrise or sunset cannot be performed with methods that, previously, only reacted to sunrise or sunset.
Photoelectric light detection has been available for utilization in apparatus,  apparatus for sixty years. Microelectronics has  have been available for decades, and the microcontroller has been available for twenty-five years. This invention does not result from material or items that have just very recently become available. Many photoelectric controls used today still use Cadmium Sulfide sensors and bimetallic thermal delay switches. Many other photoelectric controls used today use microelectronics. While some of the prior art applications utilize new technology components, they lack in innovation and novelty, even though their material cost is sufficient to support the methods and construction shown in this invention.
My invention employs, among other things, an internal xe2x80x98clockxe2x80x99, as an important method of deriving improvement and new function over previously utilized methods. Scheduling events of device activation and deactivation from the xe2x80x98clockxe2x80x99 instead of directly off the detection of light is key to the advantages which result.
As a result of the internal xe2x80x98clockxe2x80x99, one object is that every sunrise or sunset event does not have to be detected. If the performance of the apparatus does not rely on detection of every sunrise or sunset, the measurement criteria for sunrise or sunset can be increased. Preferably, the method here is to start out with loose criteria for detection, and increase the criteria to a higher level after confidence is secured. Contrasting this concept with prior art: if a sunrise or sunset is not detected, the device activation tied to that event will not be delivered. The tradeoff in the prior art is then to have lower criteria so as to not miss detection of sunrise or sunset. The disadvantage of this is that the prior art, with lower criteria, will trigger activation from false detections, such as cloud activity.
Another object is that events can be scheduled to occur before the detection of sunrise or sunset. Because of the establishment of the internal xe2x80x98clockxe2x80x99, the nominal time of the next sunrise or sunset is xe2x80x98knownxe2x80x99 by the apparatus in the present invention. This is an advantage of this invention, to be able to schedule an activation in anticipation of an event of sunrise or sunset instead of in direct reaction to it. Contrarily, in prior art, anticipation of events could not be implemented. Apparatuses  Apparatus of the prior art exhibit that the creators of these devices attempted to provide a function of this sort by utilizing a fixed time delay triggered by the direct detection of sunrise or sunset. The fixed time delay does not work because of the mechanics of earth rotation and revolution around the sun.
The earth rotates about its  an axis that is tilted 22.5 degrees from being at a right angle to the plane of the earth orbit around the sun. If the earth were not tilted, the seasons would not change and the time for sunrise and sunset would be the  substantially the same, relative to noon time, all year round, at a given latitude.
For a given latitude the amount of daylight can be calculated for a given day of the year. The maximum amount occurs on the day of the summer solstice and the minimum amount occurs on the day of the winter solstice. The day of nominally equal daylight and nighttime is on the equinox, one day in spring and one day in autumn. The identification of equinox and solstice is independent of latitude. The exception is for northern latitudes where there are several days of daylight or of nighttime, near the solstices.
It is the advantage of this invention that these seasonal drifts in sunrise and sunset do not affect the accuracy of anticipated activations, such as activation one hour before sunset, or such as one hour before sunrise. There is no reliable light sensing indication of sunrise nor of sunset, one hour before it happens. Accordingly, an apparatus of the prior art has no way of anticipating these events on that basis.
The application of these principles to deer feeders result in predictable schedules of feeding at comparable cost of apparatus based on the prior simpler methods. Light activated animal feeders have traditionally been considered products at the low-end of the cost and performance scale when compared with other timer based feeders. However, a very important aspect to be considered is that the setting of time of an electronic timer based animal feeder is  has the same disadvantage as other complex devices in today""s world. Many users shy away from electronic devices that require a set up procedure. This is true for digital watches, VCRs, and many other appliances. The light activated animal feeder has the advantage of not requiring set up. The electronic digital clock type feeders have the disadvantage of requiring the operator to go through a sequence of pushing buttons to set the time. The operator has to set the time of each activation and the run-time duration, also, through a sequence of pushing buttons.
Since light activated animal feeders require little or no programming, they should have had a better commercial success. If prior art animal feeder appliances had worked better, they would have been sought-after due to the ease of setting up and inherent lower cost. It is the belief of this inventor that the methods described here, when employed in animal feeders, will greatly improve the desirability of this class of feeder.
In the first part of this section, the first object concerns allowing for more stringent criteria on  for detection of sunrise and sunset. The methods of more stringent criteria do not include the necessity of accurate light intensity measurement. This is another advantage of this invention. The methods of detection of sunrise and sunset can be accomplished with a simple, low-cost apparatus for converting the light intensity to a numerical value. This method and apparatus of  for converting analog to digital is yet another object of this invention.
This method of converting analog to digital is also an advantageous way for an operator or user to set a programmable value in the apparatus. It is another object of this invention to use a potentiometer that can be added to the light sensing circuit, for operator input of a parameter such as a delay period. While analog to digital conversion methods of all kinds are well known to those skilled in the art, this particular combination of simple components is novel and advantageous for its low cost in an application that requires only nominal accuracy.
In the case of animal feeders, it is useful to have a push-button on the controller that is used to test the feeder operation. When the operator activates the test push-button, the feeder will run the feed motor for the duration of time for which the controller is programmed. This allows the observation of battery strength, how far the feed will spread, how much feed will be spread, and general operability.
It is advantageous for the controller to wait a few seconds before activating the motor so that the operator has time to stand back. It is yet another object of this invention to have the advantage of combining the use of one push-button for both functions of initiating a test and for setting the motor run-time duration. It is also an object of this invention to use the motor as a sounding device to warn the operator of a pending feed event, so he knows to stand back.
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.